7mm upgrade spring for sniper rifles – M160 (525 FPS)

Spring for airsoft sniper rifles. It is made of spring steel with proper heat treatment and gives the final output of about 160 m/s (525 FPS). The spring has an inner diameter of about 7.5 mm and an outer diameter of 10.2 mm. The length is 251mm.
It is therefore dimensionally suitable for most plastic basic pistons